Function covid19db::dateutil::day_to_dateutc

pub fn day_to_dateutc(day: i32) -> Date<Utc>

Convert a day to a Date<Utc>.

use covid19db::dateutil::*;
use chrono::prelude::*;

assert_eq!(day_to_dateutc(2457096), Utc.ymd(2015, 3, 14));